I have bought a laser lens to have as spare if my drive goes bad too, but I have not been needing to change it yet. There are several persons on the British AVForum that have changed on their XE1 (European XA2), and it seems like it is fairly easy to do.
Quite many HD DVD drives experience this problem after awhile, and I think it happens gradually. For some it shows itself as it will play some, but not all discs. For others it will play DVD discs, but not HD DVD discs. Others maybe have another combination of faults. The common thing is that there is disc reading problems.
As far as I have seen, everyone that changed the laser lens got their problem fixed.
Concerning lens alignment, I really don't know as I have not changed the lens myself. But it sounds like the lens changing is not a difficult procedure from the post of people who have done it. So my guess is that it fits easily into the right alignment by itself.